Titrating Oil To Make Biodiesel
by Graydon Blair of Utah Biodiesel Supply
One of the most common questions beginning biodieseler's have is how to perform a titration.
When I first learned about Biodiesel, I was taught a really easy way to do titrations.
I tried a few other methods but I keep coming back to this one because of how simple it is.
It's really easy to do and makes titrating the oil really simple.
Why Do A Titration?
Titration is just a fancy word for the process used to find out how much catalyst will be needed to make biodiesel
out of waste vegetable oil. The catalyst I use is called Potassium Hydroxide (KOH), also known as Caustic Potash.
You can also substitute Sodium Hydroxide (NaOH), also known as Lye, in place of the Potassium Hydroxide. You'll
want to titrate using the same catalyst that you'll be using when you make your biodiesel.
The "nuts & bolts" of what's going on during a titration is nothing more than seeing how much of a base it's going
to take to neutralize the free fatty acids in a sample of the oil you'll be using to make biodiesel.
We use a PH indicator called Phenol Red or Phenolphthalien. Both of these 'indicators'
are typically available at laboratory stores, pool stores, or online.
1- (3) small cups that can hold at least 50 ml of liquid
2- (3) small syringes that are metered in 1 ml increments up to 10 ml
3- (1) pint of 91% Isopropyl Alcohol
4- (1) gallon of distilled water
5- (1) gram of Potassium Hydroxide (KOH) or Sodium Hydroxide (NaOH)
6- Either Phenol Red or Phenolphthalien (both will work)
7- A sealable container that can hold at least 1 liter of liquid
8- A scale that can measure down to .05 of a gram
We now carry complete titration kits to help you get started!
Create A Stock Testing Solution
This will create a testing solution that can be used for each titration.
1- Add 1 Liter of Distilled Water to the 1 Liter container
2- Add 1 gram of KOH or NaOH to the 1 liter container
3- Shake the solution around until all of the KOH dissolves
4- Label the container TITRATION SOLUTION
NOTE: About every 90 days, remake this solution as it does "expire".
Label The Bowls
Cup 1- Titration Solution
Cup 2- Alcohol
Cup 3- Titration
Prepare The Bowls
1- Pour about 30 mL of Titration Solution into Cup #1
2- Pour about 20 mL of Isopropyl Alcohol into Cup #2
Prepare Titration Bowl
1- Add 1 mL of oil to Cup #3
2- Add 10 mL of Isopropyl Alcohol from Cup #2 to Cup #3
3- Mix the oil & alcohol together until it's a consistent solution
(sometimes heating the bowl will help it mix together)
4- Add 4 drops of Phenol Red or Phenolphthalien to Bowl #3
The Actual Titration Process
1- Suck up 10 mL of testing solution into a syringe from Cup #1
2- Drop a drop of testing solution into Cup #3, watching for a color change each time
3- Hold the bowl in your hand and swirl the solution around for 30 seconds
4- If the color change goes way, add another drop of solution from the syringe
5- Repeat steps 2-4 until the color change stay's for at least 30 seconds
6- Record on a peice of paper how many mL of solution you put in Cup #3 to keep the color change.
The Titration Calculation
If you're using KOH (Potassium Hydroxide) in the titration solution
-Add 7 to the result from step 1
If you're using NaOH (Sodium Hydroxide) in the titration solution
-Add 5.5 to the result from step 1
The result will be how many grams of catalyst you'll use per liter of oil.
100 liters of oil to be converted to biodiesel
It titrated to 4
If KOH, add 7 + 4 = 11 grams/liter X 100 liters = 1100 Grams
If NaOH, add 5.5 + 4 = 9.5 grams/liter X 100 liters = 950 grams
Add 1100 grams of KOH or 950 grams of NaOH to the methanol to make biodiesel using this oil.
Accounting For Catalyst Purity
In most cases it will be difficult to find 100% pure KOH or NaOH. Here's how to account for that.
Simply divide the "BASE" by the purity.
If KOH is used and it's 90% pure, then divide 7 by .90 (7/.90 = 7.8)
If NaOH is used and it's 95% pure, then divide 5.5 by .95 (5.5/.95 = 5.8)
Now, instead of using 7 or 5.5, use the "corrected" numbers to calculate how much catalyst is needed.
It's recommended to do a titration 3 times and record the three results. If the results are close (+/- 1), then you're set.
If it's way off, you'll want to repeat the titrations ensuring that you follow the steps exactly until your results are close.
Also, only use each syringe for one purpose. For example, use one syringe for oil only, use a separate syringe for the
titration solution, and another separate syringe for the alcohol. If you mix them it can cause inaccurate titrations.
Helpful Conversion Factors
1 Gallon = 3.785 Liters
1 Pound = 453.59 Grams
Free Fatty Acid Conversion Factor
For KOH Titration Solution: Titration Value / 1.8 = Approximate FFA%
For NaOH Titration Slution: Titration Value / 1.3 = Approximate FFA%